Electronic fan control systems and improvements thereof have been integrated into numerous vehicles to cool motor vehicle components by adjusting the rotation of a fan to control airflow about the components to be cooled. Cooling is necessary across the motor vehicle components to prevent overheating due to variances in internal and external temperatures to the motor and due to load variances placed on the vehicle and its motor components.
The fan is located near the vehicle engine to blow air drawn through engine heat exchangers, radiator, etc. over the top of the engine to carry away heat dissipated from the engine and other motor vehicle components. The fan provides cooling air and improves dissipation of heat for components such as engine coolant, transmission oil, and hydraulic oil. The primary power source for the fan is from the vehicle engine. To reach particular fan speeds and thus provide cooling the motor vehicle components can require significant horsepower draw from the engine, thus reducing engine fuel efficiency.
Electronic fan control systems process temperatures sensed at the various motor vehicle components to determine a desired rotational speed for the fan. The control system commands a clutch to drive the rotation of the fan.
In particular, U.S. Pat. No. 6,772,714 Laird et al. and entitled Electronic Fan Control, is a fan control for receiving inputs from sensors and uses the sensor inputs in determining fan speed. Fan speed in this patent can be controlled according to an alternate coolant temperature table when the PTO is activated and the transmission is in park.
With a vehicle in park, load demand variances on the motor vehicle components are non-existent. Load from an engaged PTO is also constant. With loads held constant across the motor vehicle components while the PTO is engaged and the vehicle is in park, increasing the coolant temperature causes little chance of overheating an engine when trying to reduce fan usage to reduce horsepower consumed by the fan.
What is needed is a fan control system to reduce fan speed, thus reducing horsepower consumed by a fan to reduce engine fuel consumption, but still provide cooling needs across the vehicle motor system when the vehicle is stationary or in motion. This would include selecting a minimum fan speed from calculated fan speed demands based on increased higher coolant temperatures not only when the vehicle is in park, but when the vehicle is moving.